Circuit breaker



.Fan. 12, 19370 J. w. SEAMAN 011mm BREAKER 2 Sheets-Sheet 1 Filed May 6, 1936 INSULATION INSULATION ttor meg.

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Invenr Josep h W. Seaman,

Jan. 12, 19370 J. w. SEAMAN CIRCUIT BREAKER Filed May 6, 1936 2 Sheets-Sheet 2 m 4 9 M 66 J.

Inventor: Joseph W.Seaman, b fimyl LA His Attorney.

Patented Jan. 12, 1937 cmoUrr BREAKER Joseph W. Seaman, Up rjDarby; Pa.,- assignor to General Electric Company, acorporation of New York r Application May 6, 1936', Serial No. 78,179

16 Claims. (01. 200-109) My invention relates to circuit-breakers, more particularly to circuit breakers o}? the'type provided with manual mechanism for operating the circuit controlling contacts between open and closed circuit positions and with automatic tripping means for operating the contacts to open circuit position upon the occurrence of predetermined current conditions, and has for an object the provision of a simple and inexpensive trip device for circuit breakers of this type which is reliable and positive in its operation.

Circuit breakers of the above type havev recently found considerable industrial application in connection with which a high degree of reliability is imperative. For example, a circuit breaker, in order to be entirely satisfactory, must always operate automatically to interrupt the circuit in response to, predetermined current conditions and must never operate accidentally to interrupt the circuit. In many cases, it is found necessary to mount the circuit breaker on a support which is subjected to recurrent jars or shocks. 7 For example, circuit breakers applied to the control of the various electrical circuits on a naval vessel, such'as a-battleship or a destroyer, are subjected to shocks of considerable magnitude each time a gun is fired, and it will be obvious that accidental tripping of a circuit breaker upon the occurrence of such a shock would be highly unsatisfactory.

While various types of trip devices have heretofore been employed, many of .which'are to a large extent satisfactory; much is yet to be desired in a trip device for a circuit breaker ofthis type, which trip device is extremely sensitive and which is substantially unaifected by shocks or jars imparted to the base of the circuit breaker.

Accordingly, it is a further object of my invention to provide a trip device of this character which is extremely sensitive in its operation and which is substantially shockproof. Y i

In carrying out my invention-in one form, I

provide a trip device for a circuit breaker having a tripping member biased for movement to a tripping position, which trip device comprises a-pivoted latching member having an elongate cam slot into which a portion of the tripping member extends. "The cam slot is provided with a shoulder adapted to be engaged by an extending portion of the tripping member when the latching member isin its latching position, and with an elongate portion along which the extending portion of the tripping member moves upon movement of the latching member to its releasing position. Normally, the latching member is restrained in latching position by a statically balanced trip shaft, the position of which is'substantially unaffected by shocks or jars, and means are provided for rotating the trip shaftto J release the latching member.

More specifically, the extending portion of the tripping member comprises a roller which exerts on the engaging shoulder in the cam slot a force tending to move the latching member to releas- I ing position, the relation of the shoulder and 10 the roller being such that only a small component of the total force exerted by the roller is exerted in a direction to move the latching member aboutits pivot. The rotatable trip shaft is provided with a transverse notch through which the end of the latching member moves when the: shaft is rotated to a predetermined position, and with a transversely extending operating arm, the

' shaft being journaled for rotation on an axis,

passing substantially through the center of gravity of the shaft and the operating arm.

For a more complete understanding of my invention, reference should now be had to the drawing's, in which Fig. 1 is a plan view of a circuit breaker provided with a trip device embodying my invention, the cover of the circuit breaker being removed to show the operating mechanism; Fig. 2 is an elevational view, partly in section, of the 3 circuitbreaker shown in Fig. 1; Fig. 3 is an end view of the circuit breaker; Fig, 4 is afragmem tary, sectional view taken along the line 4-4 of Fig. 3; Fig. 5 is a similar sectional view, showing the trip device in another of its operating positions; and Fig. 6 is a detail view of the shockproof, electromagnetic means provided for operating my improved trip device.

Referring now to the drawings, I have shown .my invention in one form as embodied in a trip device 10 which is applied to a three-pole circuit breaker of the type described and claimed in a 40 copending application of Winfield A. Atwood, Serial No. 29,479, filed July 2, 1935, entitled Circuit breakers, which application is assigned to the same assignee as the present invention.

As described in the said Atwood application; the

circuit breaker comprises a plurality of individual single-pole-units ll, l2, and I3, respectively, the bases of which are rigidly secured to-. gether in side by-side relation, with suitable insulating barriersl4 and, I5 interposed therebetween. The single-pole units II, l2, and I3 areidentical in construction, .and accordingly,

onlyfthe single-pole unit II will be described in detail. -As shown best in Fig. 2, this single-pole unit ll comprises a base member I6, preferably formed of insulating material and provided with ahousing l1 within which is located a circuit interrupter ll of the compression chamber type, having a fixed contact l9 and a movable contact 29.

Secured to the base It adjacent the housing I1, is a U-shaped frame 21 which supports the operating mechanism. For the purposesof the present invention, this operating mechanism may be briefly described as comprising a pair of overcenter springs 22, the respective adjacent ends of which are connected to the opposite ends of a pin 23 which extend through a slot (not shown) in the extending end of the movable contact 29, the other ends of the springs 22 being connected to a pin 14 which is supported on the free ends of a pair 'of levers 25, the opposite ends of which are pivotally mounted on a fixed pin 29. The pin 24 extends through a slot (not shown) in an operating member 21 which is pivotally mounted on a pin 29 supported by the frame 2|.

.Also pivoted on the pin 29 is a tripping member 29 which is normally held in the position shown in Figs. 1 to 4 against the bias of a tripping spring 99 by my improved trip device [9 in a manner to be more fully described later. This tripping member 29 is provided with an extending finger II (Figs. 4 and arranged to engage a crosswise extending portion 32 of a guide link 33, one end of which is pivotally supported on the pin 29, and the other end of which pivotally engages the pin 23.

As stated above, the single-pole units ll, I2, and I3 are identical in construction and, as shown, the operating member 21 of the unit I2 is provided with an insulated handle 34, the operating members 21 of the three single-pole units being connected together by means of an insulated crossbar 95. It will be apparent now that when the handle 34 is moved to rotate the operating member 21 of the single-pole unit l2 about its pivot,-the crossbar 35 will effect rotation of the operating members 21 of the units H and I9 so as to carry the springs 22 of the three units overcenter relative to the respective pivot pins 29. Accordingly, the movable contacts 29 of the three units will be simultaneously operated between open and closed circuit positions with a snapaction, as is more fully described in the above referred to Atwood application.

A second insulated crossbar 99 which likewise extends across the three single-pole units is connected to the tripping members 29 and is provided with an extending finger 31. Thus, it will be seen that the finger 31, together with the cross bar 39 and the tripping members 29, constitutes a tripping member for the circuit breaker which is biased to tripping position by the springs 99, the position of this tripping member being controlled by my improved trip device in the manner now to be described.

As shown best in Figs. land 3, my improved trip device I9 is supported on a U-shaped frame which comprises a pair of spaced apart plates 98 and 39 secured to the base l5 of the center unit II, the upwardly extending ends of the plates 39 and I9 rotatably supporting a balanced trip shaft 49. This trip shaft 49 is provided intermediate the plates 39 and 39 with a transversely extending arm or trip paddle 4i, and the ends of the shaft which'extend outwardly over the units II and I! carry transversely extending paddles or arms 42 and 43,

enemas preferably formed of insulating material. Adlacent the arm 4|, a portion of the trip shaft 49 is cut away to provide a transversely extending notch 44.

Arranged for co-operation with the trip shaft 49, I provide a latching member 45 which is pivotally mounted on a pin 45 carried by an extending portion of the plate 39 (Figs.'4 and 5), the free end of the latching member 45 comprising a latching tip 41. As shown, the latching member 45 is in alignment with the notch 44, and accordingly, the latch tipv 41, which normally engages the periphery of the shaft 49, as shown in Fig. 4, is movable through the notch 44 to the releasing position shown in Fig. 5 when the shaft 49 is rotated to the position there shown. Intermediate its ends, the latch member 45 is provided with an elongate cam slot 48 into which extends a roller 49 car ried by the finger 31, which finger, as described above, constitutes a portion of the trippingrnemher for the circuit breaker.

As shown, the cam slot 45 is provided with a shoulder 59 adapted to be engaged by the roller 49 when the latching member 45 is in its latching position, shown in Fig. 4, and an elongate portion 5| along which the roller 49 moves as the latching member 45 moves to the releasing position shown in Fig. 5. Likewise, the cam slot 48 is provided with a resetting portion or shoulder 52, the function of which will be more fully described hereinafter.

It will be apparent that in the latching position shown in Fig. 4, the roller 49 exerts a force on the shoulder 50 tending to rotate the latching member 45 to the releasing position shown in Fig. 5. The shoulder 59, however, is arranged at such an angle relative to the path of movement of the roller 49 and to the pivot 45 that the greater portion of the force exerted on the shoulder 59 is absorbed by the pivot pin 45, only a small component of the total force being in a direction to rotate the latch member 45. Furthermore, it will be seen that the force exerted on the shaft 49 by the latch tip 41 constitutes only a fraction of the rotative component exerted on the shoulder 59, since the latch tip 41 is at a greater distance from the pivot pin 49 than is the shoulder 59. Because of the relatively light load imposed on the shaft 49 by the latch tip 41, a high degree of sensitivity is obtained, while providing positive latching of the finger 31.

In order that the trip device [9 shall be substantially shockproof, the shaft 49, which constitutes the primary latching member, must be substantially unaffected by shocks imparted to the circuit breaker base. Since the pivot pin 46 and the portion of the shaft 49 adjacent the notch 44 are supported on the same supporting member will be caused by shocks or jars imparted to the circuit breaker base, and in order that such shocks may not cause rotation of the shaft 49, I construct the shaft 49 and the arms 4|, 42, and 43 as a statically balanced unit journaled in the plates 98 and 39, for rotation about a longitudinal axis passing substantially through the center of gravity of the balanced unit. It will of course be understood that perfect static balance is rather difiicult to obtain, and accordingly, shocks of very great magnitude may cause a slight rotation of the shaft 49. In order that a series of such excessive shocks may not cause either thermal or magnetic, may be provided for cated, as shown best in Fig. 3, andis provided,

' with a pivot pin 58 (Fig. 6) on which is'mounted a gradual step-by-step movement of the shaft 40 to its releasing position, I provide a resetting spring 53 (Figs. 1 and 3)-, which is efiective automatically ,to return the shaft"40 to its. fully latched position, following any-slight rotational movement thereof 'due to such shocks.

Although-the latching member 45" and the shaft 49- may be arranged in any desired. manner so that rotation of the shaft releases the latch tip 41 for movement .through the notch 44,

. I have shown for purposes of illustration a. preferred arrangement which is specifically described and claimed in the copending application of Robert W. Smith, Serial No. 78,177, filed May 6, 1936', entitled Circuit breakers", which application-is assigned to the samegassignee as the present invention. As described in the said Smithapplication, the pivot pin 46 and the trip shaft 49 are so arranged that the latch tip 41 moves along an arc passing'substantially through the center of' the shaft 40, the notch 44 being cut back slightly past the center-of the shaft so as to permit movement of the .latch tip 41 along,

the said are when the shaftis rotated to its releasing position. Thus, the latch tip 4'! engages the periphery of the shaft 40 substantially tangentially, and the force exerted thereby on the;

1 shaft 40 is along a substantially radial line so that no rotative movement is exerted on they shaft 49 by the latch tip 4|. Consequently, in order to rotate the shaft 40 to its releasing posi-. tion, only the force of thespring 53 and the I slightfrictional force between the latchtip 41 and the shaft .49 need be overcome. a,

While any suitable current responsive means,

engaging on'eor more of the arms 4|, 42, and 43 to rotate the trip'shaft 40,,1 have. shown associated witheach pole of the circuit breaker,

shockproof electromagnetic means of the type described and claimed in the above referred-to I Smith application.

I As shown best in Fig. 6, each electromagnetic device comprises a magnetizable core. 54 provided' withpole pieces 55 'and 56, the pole piece 55 being mountedon a support 51 secured to'the base of the circuit breaker, the support 51 for the pole unit |2 being formed'integrally with the supporting plate 38. The pole piece 56 for each of the' electromagnetic devices is bifurfully explained in the above'Smith application," the armature 59 [is pivoted about its center of gravity so as to be substantially unaffected by shocks transmitted through the pivot pin 58,

and is provided with a shock. spring 64, one end "of which is secured to the armature by a screw 65 and the other end of {WhiCh is maintained under tension closelradjacent the lower end of the armature bya stop screw 66'. As shown'gthe biasing spring Bk-tends to rotate the armature 59 away, from the pole piece 55 .and 'fiward a fixed stop'6'l which is formed integrally with the support 51. The shock spring 64,,however,

is arranged to 'engagejthe stop6l to hold the armature out. of direct engagement therewith I v 'so as to prevent the transmission'of; shocks from v restrained against such. rotation; however, so 75 links is reversed, and the upper ends I links are thereupon rotated in a counterclock which position the operating the stop 61 to the armature 59. Extending outwardly from each of the armatures 59 is an adjustable screw 68 arranged to engage the associated one of the arms 4i, 42, and 43 to rotate the trip shaft 40 when the armature 59 is attracted from the biased position shown in Fig. 6 upon energization of a winding 69 which surrounds the core 54. I

One end of the energizing winding 69, as

shown best in Fig. 2, isconnected to the terminal 10 screw- 63,which., in turn, is connected by a conductor 10 to an external terminal ii, and the other end of the winding 69 is connected (Fig. 6)

to a flexible conductor 12 leading to the asso through each pole of thecircuit breaker may be traced '(Fig. 2) from the terminal screw ll through the conductor.lil, the terminal screw 633, the winding 69, the flexible conductor 12, the fixed. contact 20, the movable contact i9, and by 20 way of a. conducting strap 13 to another external terminal 14.

, ciated movable contact 20. Thus, the circuit. 15

It is now believed that a complete understanding of my invention may be had from a' 5 description of the operation. 'InFigs. 1 to inclusive, the circuit breaker is shown -in'its closed circuit position, and it will be assumed that an overloadoccursin' the center" pole unit I 2 of sufficient magnitude to energize the associated winding 69 so as to attract the lower end of the armature 59 from the biased position shown best in Figs. 2,/4, and 6, to the attracted position I shown in Fig. 5; As the armature moves to this position, the, screw 68 carried by the armature 59 engages the trip arm 4| and 5 rotates I} the shaft 49 to the releasing position shown. in Fig. 5, whereupon theforce exerted by the roller 49 on the shoulder 59 rotates the latch member 45 to the releasing position 'shown in Fig. 5, the latch tip 41 moving through the slot rlnsulated crossbar 36 are moved to the position sliownin Fig. 5, the, tripping members 29 associated with. each pole of the circuit breaker are rotated ina clockwise direction about the pivot pin 28, and the extending finger 3| on each of these tripping members engages the cross portion 32 to operate the links .33 and the movable contacts 20 to the open circuit position shown in.Fig.5.' l

- A; the movable contacts 20 move to the open X circuit position, it will be seen that the lower center relative to the pivot pin 26, and accord ingly, the force exerted by the springs on the,

of these end of each overcenter spring 22 'is carried overa wise direction to move the operating members so 21, the insulated crossbar 35,.and the operating handle 34 to the vmidposition shownin Fig. 5, in

the insulated crossbar 36.

It will be understood of course that as soon all of the current responsive devices .will be de-- energized, andaccordingly, the armatures 59 springs 6h Thus; the trip shaft 40 is released -for rotation in a counterclockwise direction to: its latching position under the force exerted by the resettingspring 53. .The shaft 40 will be will be returned 'totheir biased positions by the 70 handle 34 engagesf -the position shown in Fig. 4, and this may be accomplished simply by rotating the operating handle 34 in a counterclockwise direction from the position shown in Fig. 5 so as to'press down-.

wardly on the crossbar I! and rotate the tripping member, which includes the finger 31, in a counterclockwise direction about the pivot pin As the crossbar 3' and the finger 31 aremoved in this direction, it will be seen that the roller 49 moves along the portion ll of the cam' slot 48 until it engages the resetting shoulder 52, whereupon a cam action is exerted on the shoulder 51 tending to rotate the latch member 45 in a counterclockwise direction from the position shown in Fig. 5. the roller II in its extreme position engaging the tip of the wetting portion 52. As soon as the latch tip 41 moves out oi theslot 44, the resetting spring 53 rotates the trip shaft 40 to the position shown in Fig. 4 and upon release 0! the operating handle 34, the tripping springs 30 will tend to rotate the latch finger 31 in "a clockwise direction about the pivot 20. Movement ,of the latch finger IT in this direc-- tion, however, is prevented by engagement of the roller 49 with the shoulder Ill, and clockwise rotation 01 the latching member 45 under the force e lerted on the shoulder." will be prevented to engagement orth latching tip 41 with-the periphery of the trip shaft lll. Accordingly, the

trip device will assume the latched position shown in Fig. Y thereafter be closed simply by rotating the operating handle 34 in a clockwise direction tothe position shown in Pig. 4.

While I have shown a particular embodiment of my invention, it will be understood, oteourse, that Ido not wish to be limited thereto, since modifications may be made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope or my invention. fWhatIclaim asnewand desiretosecureby Letters Patent 01 the United States is:

l. A trip device for a circuit breaker having a tripping member biased for movement to a tripping position, said trip device comprising a pivot-- ed latch member movable between latching and releasing positions having a cam slot into which a latching portion of said trlpp it member extends, said cam slot including a shoulder engageable by said'latching 'portion to restrain said tripping member against movement to said tripping position when said latch member is in said latching position and an elongate portion along whichsaid latching portion moves to said tripping position when said latch member is moved to said releasing position. said latching portion exerting a force on said shoulder tending to move said la current responsivemeans normally restraining said latch member in said latching position for releasing -said latch member for movement to said releasing position, whereupon said tripping member moves to said tripping position. i

2. A trip device (or a circuit breaker having a tripping member biased for movement to a tripping position, said trip device comprising a pivoted latchomembermovable between latching and releasing positions a cam slot into which 4, and the circuit breaker may member to said releasing position, and

ping position when said latch member is ,in said 5 latching position and an elongate portion along which said latching portion moves to said trip ping'position when said latch member is moved to said releasing position, said latching portion exerting a force on said shoulder tending to move 10 said latch member to said releasing position, and

i current responsive means normally restraining said latch member in said latching position for releasing said latch member for movement to said releasing position, whereupon said tripping 1| member moves to said tripping position, said cam slot including a resetting portion engageable by said latching portion of said tripping member upon return movement of said tripping member for returning said latch member to said latching position. i

3. A trip device for a circuit breaker having a tripping member biased for movement to a tripping position, said trip device comprising a latchi ing roller carried by said tripping member, a a pivoted latch member movable between latching and releasing positions having an elongate cam slotinto which said roller extends, said camslot including a shoulder engageable by said roller to restrain said tripping member against movement a when said latch member is in said latching position and a portion along which saidroller moves to said tripping position when said latch member is moved to said releasing position, said roller when engaging said shoulder exerting a. force tending to move said latch member to said releasing 'posit ion, andfcurrent responsive means normally restraining said latch member inisaid latching position for releasing said latch member ior'movement to said releasing position, where- 40 upon said tripping member is released for movement tosaid tripping position.

4. A trip device for a circuit breaker having a tripping member biased for movement to a tripping position, said trip device comprising a a latching roller carried by said tripping member, a. pivoted latch member movable between latching and releasing positions having an-elongate cam slot into which said roller extends, said cam slot including a shoulder engageable by said roller 5.

to restrain said tripping member against movement whensaid latch member is in said latching position and a portion along which said. roller moves to said tripping position when said latch member-is moved to said releasing/position, said a shoulder beingv formed at an angle such that the major portion of the force exerted by said roller when in engagement with said shoulder is absorbed by the pivot of said latch member,

a small component of said iorce tending to move Q said latch member to said releasing position, and current responsivemeans normally restrainingsaid latch member in said latching position for releasing said latch member for movement in accordancewith said smallcomponent of force, 5|

whereupon said tripping member is released for movement to said tripping position, to

5. A trip device or a circuit breaker having a V tripping member biased for movement to a tripping position, said trip device comprising a latch- 7.

ing roller carried by said tripping member, a pivoted latch member movable between latching and releasing positions having an elongate cam slot into which said roller extends, said cam slot including a shoulder engageable by said roller 7 to restrain said tripping member against move-i ment to said tripping position when said latch member is in said latching position and a portion along which said roller moves to said triptripping position for retm'ning said latch member to 'said latching position.

8. A trip device for a circuit breaker having a tripping member biased for movement to a triproller upon return movement of-said tripping position, whereupon said tripping member moves ping position when said latch member is moved ping position, said trip dev ce compr s n a to said releasing position, said roller exerting pivoted latch member movable between latching a force on said shoulder tending to move said and releasing positions having a cam slot into latch member to said releasing position, and w c a tching p t on of said pp member current responsive means normally restraining extends. said cam slot including a shoulder ensaid latch member in said latching position for gageable by said latching portion to restrain realsing said latch member for movement to said ppi member against ov me t to said said releasing position, whereupon said tripping tripping position when said latch member is in member moves to said tripping position, said said latching P t and an elongate P o cam slot. including a portion engageable by said along which'said la hing portion moves to said tripping position when said latch member is member for returning said latch member to said moved o said releasing Position, said latching latching position, a portion exerting a force on said shoulder tending 6. A trip device for a circuit breaker. having to move said latch mmber to id r l in a tripping member biased for movement, to a P n, shookpro L s-sabl rest ans tripping position, said trip device comprising a for said latch member inc g a rotatable latch'member, meanspivotally mounting said shaft v n 8 r n ve ly extending notch latch member for movement between latching E 811d tmnsversely extending Operating and releasing positions, current respbnsive arm, means 11101111151118 said shaft for rotation meansnormally engaging an end of said latch about an axis Passing through the center of member remote from said pivot means for regravity of said shaft and said operating amt straining said latch member in said latching whereby substantially no rotative movement of position, said latch member-having an elongate i shaft is Produced y parted to cam slot intermediate said pivot means and said 531d mounting m ns. 11 P r io f d ft remote end into which a latching portion" oi \adjaccnt d notch normally a ing said latch ,said tripping member extends, said cam slot member to restrain saidlatch member'in said including a shoulder engageable by said latching latching Position. a d ourrentresponsive means portion for restraining said tripping member 1501 engaging said operating arm to rotate said against nt t Said tripping position when shaft to a position in which said latch member said latch member is in said latching position is released for movement t ou h said notch.

whereupon said tripping member is released for and an elongate portion along which said latching portion moses to said] tripping position when movement to said tripping position.

said latch member is moved t said releasing 9. A trip device for a circuit breaker having a fi said latching portion exerting r ni tripping member biased for movement to a tripon said shoulder tending to move said latch Ping I Q s d p device comprising a member to said releasing position and said c'urlatchlng o ler carried by saidtripping member, rent responsive means upon the occurrence of I pivoted latch mber movable between latchpredetermined current conditions releasing said 8 and releasing positi ns having an enlongate latch member for movement to said releasing cam slot mm which said r0119! extends, d cam I slot including a shoulder engageable by said to said tripping position. v

'1. A trip device for a circuit breaker having a tripping member biased for movement to a trip ping position, said trip device comprising a latching roller carried by said tripping member, a latch member,-means pivotally mounting said latch member for movement between latching and releasing positions, current responsive means normally an'end of aid latch member remote from said pivot means for restraining said latch in her in said latching position, said latch mem \having an elongate cam slot in termediate said pivot means and-said remote sai rouei-ror restraining said tripping member against movement to said tripping position when said latch member is in said latching position and a portion along which said roller moves to said tripping position when said latch member is moved to said releasing position, said roller exerting a force on said shoulder tending to move said latch member to said releasing position and said current responsive means upon the occurrence oi predetermined current conditions releasing said latch member for movement to said rel position, whereupon said trip-- ping'member moves'to said tripping position, and resetting means includins a portion of said cam slotengageable by said roller upon return movement of said tripping member from said roller to restrain said tripping member against movement when said latch' member is in said latching position and a portion" along which said roller moves to said tripping position when said latch member is moved to said releasing position, said roller when engag n said shoulder exerting a force tending to move said latch member to said releasing posit on, shockproot, releasable restraining means for said latch member including a rotatable shaft having a transversely extending notch therein and a transversely extending operating arm, means mounting said shaft for rotation about an axis passing'through the center of gravity of said shaft andsaid operating arm whereby substantially no rotative movement ofsaid shaft is produced by-shocks imparted to said mounting means, a portion of said shaft adjacent said notch normally said'latch latching position, and current responsive means {or said operating armto rotate said "shaft to a position in which said latch member is irdeased for movement through said notch, whereupon said tripping member is released for movement to said tripping position.

10. A trip device for a circuit breaker having a pivoted latch member movable between latch-- in:andrelcal-ingpcnitioushovin:an lilllmto member to restrain said latch member in said cam slot into which said roller extends, said cam slot including a shoulder engageable by said roller to restrain said tripping member against movement when saidlatch'member is in said latching position and a portion along which said roller moves to said tripping position when said latch member is moved to said releasingpbsition, said roller when engaging said shoulder exerting a force tending to move said latch member to said releasing position, shockproof, releasable restraining means for said latch member including a rotatable shaft having a transversely extending notch therein and transversely extending operating arm, means mounting said shaft for rotation about an axisrpassing through the center of gravity of said shaft and said operating arm whereby substantially no rotative movement of said shaft is produced by shocks imparted to said mounting means, means biasing said shaft to one position in which a portion of said shaft adi acent said notch engages said latch member to restrain said latch member in said latching position, and current responsive means for engaging said operating arm to rotate said shaft to a second position whereby said latch member is released for movement through said notch to release said tripping member.

11. A trip device for a circuit breaker having a tripping member biased for movement to a tripping position, said trip device comprising a latching roller carried by said tripping member, a pivoted latch member movable between latching and releasing positions having an elongate cam slot into which said roller extends, said cam slot including a shoulder engageable by said roller to restrain said tripping member against movement when said latch member is in said latching position and a portion along which said roller-moves to said tripping position when said latch member is moved to said releasing position, said'roller when engaging said shoulder exerting a force tending to movesaid latch member to said releasing position, shockproof, releasable restraining means including. a statically balanced rotatable shaft having a transversely extending notch therein and a transversely extending operating and, means biasing said shaft to one position in which said latch member is restrained in said latching position by a' portion of said shaft adjacent said notch, and current responsive means for actuating said operating arm to rotate said shaft to a second position whereby said latch member is released for movement through said notch to release said tripping member.

12. A trip device for a circuit breaker comprising a latch member movable between latching and releasing position and shockproof, releasable restraining means for said latch membe including a rotatable shaft having a transversely extending notch therein and a transversely extending operating arm, means mounting said shaft for rotation about an axis passing through the center of gravity of said shaft and said operating arm whereby substantially I no rotative movement of said shaft is produced by' shocks imparted to said mounting means, a portion of said shaft adjacent said notch normlly engaging said latch memberv to restrain said latch member in latching position, and curre t responsive means for engaging said operating arm to rotate said shaft to a position in which said latch member is released for movement through said notch to said releasing position. i

13. A trip device for a circuit breaker comprising a latch membermovable between latching and releasing position and shockproof, releasable restraining means for said latch member including a rotatable shaft having a "in which a portion of said shaft adjacent said notch engages said latch member to restrain said latch member in said latching position, and current responsive means for engaging said operating arm to rotate said shaft to a second position in which said latch member is released for movement-through said notch to said releasing a position.

14.- A trip device for a circuit breaker comprising a latch member movable between latching and releasing positions, a support on which said latch member is pivoted for movement, and shockproof, releasable restraining means for said latch member including a rotatable shaft having a transversely extending notch therein and a transversely extending operating arm, said shaft being 'ournaled in said support for rotation about an axis passing through the center of gravity of said shaft and said operating arm whereby substantially no rotative movement of said shaft is produced by shocks imparted to said support, means biasing said shaft to one position in which said latch member is restrained in said latching position by a portion of said shaft adjacent said notch, and current responsive means for engaging said operating arm to rotate said shaft to a second'position in which said latch member is released for movement through said notch to said releasing position. b

15. A trip device for a multipole circuit breaker comprising a latchmember movable between latching and releasing positions, shockproof, releaseable restraining means for said latch member including a shaft extending across at least two of the poles of said circuit breaker and having a transversely extending notch therein, .a plurality of transversely extending operating arms for said shaft, means mounting said shaft for rotation about an axis passing through the center of gravity of said shaft and said operating arms whereby substantially no rotative movement of said shaft is produced by shocks imparted to said mounting means, means biasing said shaft to one position in which said latch member is restrained in said latching position by a portion of said shaft adjacent said notch,

. and current responsive means associated with at least two poles of said circuit breaker for actuating said operating arms to rotate said i shaft to a second position in which said latch member is released for movement through said notch to said releasing position.

16. A trip device for a multipole circuit breaker having a tripping member biased for movement to a tripping position, said trip device comprising a latching roller carried by said tripping member, a supporting frame, a latch member pivotally mounted on said frame for movement I and having a transversely extending notch i,

to restrain said tripping member against movement to said tripping position when said latch member is in said latching position and a portion along which said roller moves to said trippingposition when said latch member is moved to releasing position, said roller when engaging said shoulder exerting a force tending to move said latch member to said releasing position,

shockproof, reieaseablerestraining means for said latch member including a shaft extending across at least two poles of said circuit breaker therein; a plurality of transversely extending operating arms on said shaft, said shaft being journaled in said supporting'frame for rotation about an axis passing through the center of gravity of said shaft and said operating arms whereby substantially no. rotative movement of said shaft is produced by shocks imparted to said frame, meansbiasing said shaft to one position in which said latch member is restrained in said latching position-bye. portion of said shaft adjacent said notch, and a plurality of current responsive devices individually associated with ,at least two poles of said circuit breaker 'for actuating said operating arms to rotate said shaft to a second position inwhich said latch member is released for movement through said tripping member.

notch to release said I v I JOSEPH W. SEAMAN. 

